Shooting at 50p at DVinfo.net

Alan Grove · June 29th, 2019, 07:41 AM

Hi Guys, I have up to now been recording in 1080/50i at 25 fps with 1/50th shutter @ bitrate of 25mbs.
I use a timeline of the same settings but from time to time I use higher frame rates... (50p) for some smooth half speed slow-mo. According to the spec of my camera recording at 50p gives me double the bitrate @ 50mbs. Personally I cant see any difference in quality? So my question here is... Is there any disadvantage to always record in 50p, drop it on the timeline and continue to edit on a 25fps timeline? Also, should I stick to the 180 rule by setting 100 shutter to match 50fps or just leave shutter at 1/50th as it looks the same?
I am thinking that I have the ability to use slow-mo at any point on the timeline if this makes sense?

Basically, (apart from less space on card) is there a problem leaving my settings at XAVC S 1920 x 1080 @ 50p= 50 Mbps and recording at all times?

Many thanks

Christopher Young · June 29th, 2019, 11:31 AM

50p on a 25p timeline at double the bit rate is good. Do it all the time. Basically I shoot everything at 50p, UHD and HD and sometimes even 4k. Most of it UHD though. From that I can output almost any frame rate needed. I edit UHD mostly on an HD timeline asit gives me the ability to re-frame from UHD anywhere down to an HD 25% crop with no quality loss. 50p gives me the choices of outputting 25p or 50p or even 720p at 25 or 50p and it all works fine. For broadcast it's mainly HD 50i output and 50i from 50p works very well. Plus as you said 50p gives great 50% slo-mo when half speed conformed to 25 fps on a 25p timeline.

As regards shutter speed the old film rule of double the frame rate, i.e. 24 fps and a shutter of 48th sec was necessary to help smooth motion. The fact that 50 fps is well outside the persistence of human vision there is no need to go to 100th. 50th sec works fine. If on high speed subject matter then yes a 100th sec shutter will sharpen that up somewhat if you know you want to slow that footage down in post.

The only downside I'm aware of is obviously you chew through more card and storage space but if that is not an issue I would suggest shooting 50p gives you a heap sight more delivery options. +1 for 50p in my book.

Chris Young
Sydney

Alan Grove · July 3rd, 2019, 01:49 AM

Thanks Chris, that is really helpful.
Thank you for taking the time to help me get the answers to my question.

Christopher Young · July 7th, 2019, 09:00 AM

No problems Alan! I'm from just over the River Severn originally, a Bristolian, ex Beeb. As students we used drive over to Cardiff to chase your girls and have pint :))

Chris Young

June 29th, 2019, 07:41 AM	#1
Alan Grove New Boot Join Date: Apr 2017 Location: Cardiff Posts: 8	Shooting at 50p Hi Guys, I have up to now been recording in 1080/50i at 25 fps with 1/50th shutter @ bitrate of 25mbs. I use a timeline of the same settings but from time to time I use higher frame rates... (50p) for some smooth half speed slow-mo. According to the spec of my camera recording at 50p gives me double the bitrate @ 50mbs. Personally I cant see any difference in quality? So my question here is... Is there any disadvantage to always record in 50p, drop it on the timeline and continue to edit on a 25fps timeline? Also, should I stick to the 180 rule by setting 100 shutter to match 50fps or just leave shutter at 1/50th as it looks the same? I am thinking that I have the ability to use slow-mo at any point on the timeline if this makes sense? Basically, (apart from less space on card) is there a problem leaving my settings at XAVC S 1920 x 1080 @ 50p= 50 Mbps and recording at all times? Many thanks

June 29th, 2019, 11:31 AM	#2
Christopher Young Trustee Join Date: Apr 2008 Location: Sydney Australia Posts: 1,571	Re: Shooting at 50p 50p on a 25p timeline at double the bit rate is good. Do it all the time. Basically I shoot everything at 50p, UHD and HD and sometimes even 4k. Most of it UHD though. From that I can output almost any frame rate needed. I edit UHD mostly on an HD timeline asit gives me the ability to re-frame from UHD anywhere down to an HD 25% crop with no quality loss. 50p gives me the choices of outputting 25p or 50p or even 720p at 25 or 50p and it all works fine. For broadcast it's mainly HD 50i output and 50i from 50p works very well. Plus as you said 50p gives great 50% slo-mo when half speed conformed to 25 fps on a 25p timeline. As regards shutter speed the old film rule of double the frame rate, i.e. 24 fps and a shutter of 48th sec was necessary to help smooth motion. The fact that 50 fps is well outside the persistence of human vision there is no need to go to 100th. 50th sec works fine. If on high speed subject matter then yes a 100th sec shutter will sharpen that up somewhat if you know you want to slow that footage down in post. The only downside I'm aware of is obviously you chew through more card and storage space but if that is not an issue I would suggest shooting 50p gives you a heap sight more delivery options. +1 for 50p in my book. Chris Young Sydney

July 3rd, 2019, 01:49 AM	#3
Alan Grove New Boot Join Date: Apr 2017 Location: Cardiff Posts: 8	Re: Shooting at 50p Thanks Chris, that is really helpful. Thank you for taking the time to help me get the answers to my question.

July 7th, 2019, 09:00 AM	#4
Christopher Young Trustee Join Date: Apr 2008 Location: Sydney Australia Posts: 1,571	Re: Shooting at 50p No problems Alan! I'm from just over the River Severn originally, a Bristolian, ex Beeb. As students we used drive over to Cardiff to chase your girls and have pint :)) Chris Young